The field of the present invention is frame rail and bumper beam combinations for automotive vehicles. More particularly, the field of the present invention relates to an arrangement of a frame rail and bumper beam combination for an automotive vehicle wherein in a frontal crash the bumper beam will deform in a manner to provide a predetermined deceleration response.
Providing bumpers on the front end of automotive vehicles is well known. Bumpers were initially provided on the front end of vehicles to reduce damage from frontal collisions. In subsequent years, the protection afforded by the bumper to the vehicle was diminished in favor of utilizing the bumper to add to the aesthetics of the vehicle. In response to the diminished crash protection previously afforded by many bumpers, federal regulations were promulgated to provide for bumpers to meet certain minimum crash worthiness standards in relatively low speed crashes.
It was initially thought that a vehicle must be made as structurally sound as possible to maximize the protection to occupants in a frontal crash. Over a period of time it was discovered that in crashes, structural rigidity alone did not maximize vehicle occupant safety. For maximum protection in frontal crashes not only must there be high strength, but the bumper must deform in such a manner to minimize the amount of deceleration experienced by the vehicle occupant. Automotive designers now incorporate bumpers and the attached frame rails as part of the total safety system in the vehicle.
In the most recent two decades passive restraint systems have been added to automotive vehicles to further protect occupants in frontal collisions. The most widely accepted passive restraint system for front seat occupants is the supplemental inflation restraint (SIR), commonly referred to as an air bag. In a SIR system, accelerometers or other kinematic sensors, are placed on the vehicle to provide a signal to an inflator device when certain predetermined deceleration conditions are experienced. In a frontal crash, the signal will initiate a gas generating or gas dispensing reaction, which rapidly inflates a fabric envelope that cushions rapid forward movement of a front seat occupant, thereby limiting the deceleration of the front seat occupant. Deployment of SIRs in automotive vehicles has substantially reduced fatalities and serious injuries to vehicle occupants. However, installation of SIRs in automotive vehicles has further complicated the design criteria for automotive bumpers.
Automotive bumpers are designed in accordance with government regulations to minimize damage to the vehicle in low speed collisions. Automotive bumpers must also be designed to contribute to the safety of vehicle occupants by being part of the total energy absorption of the vehicle front end in a crash. It is desirable to provide an automotive bumper that meets the above criteria and has a discriminated deceleration response in low and high speed vehicle crashes.
In a low speed crash, it is desirable that the SIR system not deploy. Therefore, to prevent deployment of the SIR, the deceleration response given to the accelerometer must be such that the accelerometer can properly discriminate it from a high speed collision deceleration response.
In a high speed crash, it is desirable for the SIR to deploy. Therefore, the deceleration response from the bumper to the accelerometer must allow the accelerometer to discriminate it from a low speed deceleration response in order to signal the inflator to operate.
The bumper must be strong enough to prevent damage to functioning components such as headlamps and hood latches in a low speed crash situation.
It is desirable to provide a front bumper which, in a low speed crash will deform in a manner to prevent the accelerometer from experiencing a high deceleration response in order to prevent subsequent SIR deployment.
To make manifest the above noted and other manifold desires, the revelation of the present invention is brought forth. The present invention provides the freedom of an automotive bumper with appropriate high strength characteristics in low speed crashes while at the same time having a predetermined deformation which allows discrimination in the deceleration response experienced by an accelerometer on a vehicle equipped with an SIR system.
The present inventive arrangement is not bound by a specific means of connection of the frame rail to the bumper beam, but can encompass various connective schemes.
In a preferred embodiment the present inventive arrangement provides a frame rail for connection with the remainder of the chassis of the automotive vehicle. The frame rail extends in a generally longitudinal direction from the chassis. A bumper beam is provided having a tubular cross-sectional shape. The bumper beam has a first section connected with the frame rail. First upper and second lower surfaces extend between the front and rear ends of the bumper beam. The first and second surfaces have vertically and laterally aligned first, second and third cutouts. The outer cutouts are generally circular and have an axis that extends along the neutral axis of the bumper beam, which essentially intersects the centroid of the bumper cross section. The cutouts allow the bumper beam to plastically deform in a frontal direction.
In a very low speed crash, the structural integrity of the bumper beam is essentially unabated. In a crash with a change in velocity below the no-deploy threshold of the SIR, the bumper beam will deform in such a manner to provide a deceleration response to an accelerometer which will signal the inflator device to not deploy the SIR system.
In a higher speed frontal collision the frame rail bumper beam arrangement will provide a deceleration response of sufficient magnitude in a sufficiently short time interval to allow the accelerometer to signal the inflator device to operate.
The sizes and relative positions of the cutouts improve the discrimination of high speed crashes with obstacles which are relatively compliant during the early part of a crash, but become more rigid as the crash progresses and the vehicle slows down. This type of phenomena is evident during frontal crashes between vehicles and during crashes with deformable barriers such as those used in certain vehicle performance tests. High speed collisions with deformable objects can create deceleration responses which may be less severe than those with rigid objects at low speeds during the early interval of a crash. Low speed crashes with rigid objects are often used to establish the no-deploy threshold of a SIR. Therefore, certain classes of high speed crashes may not result in SIR deployment until late in the event. Such circumstances may result in diminished protection to vehicle occupants.
It is a feature of the present invention to provide a frame rail bumper arrangement wherein the deceleration response of the bumper beam in a frontal crash is such that an accelerometer can discriminate between low speed and high speed crashes.
It is another feature of the present invention to provide a frame rail bumper beam arrangement as described above wherein the bumper beam has sufficient strength to protect the vehicle from damage in very low speed crashes.
The above noted features and other advantages of the present invention will become apparent to those skilled in the art as the invention is further explained in the accompanying drawings and detailed description.